Cable slack control device for clamshell rigs



March 3; 1970 W. J. RODGERS ET AL CABLE SLACK CONTROL DEVICE FOR CLAMSHELL RIGS 2 Sheets-Sheet 1 Filed June 6, 1968 INVENTORS: WILLIAM J. RODGERS THOMAS H HUGHES March 3, 1970 w. J. RODGERS ETAL 3,498,472

CABLE SLACK CONTROL DEVICE FOR GLAMSHELL RIGS Filed June 6, 1968 2 Sheets-Sheet 2 INVENTORS WILLIAM J. RODGERS THOMAS Q HUGHES United States Patent U.S. Cl. 212--8 8 Claims ABSTRACT OF THE DISCLOSURE This invention is directed to a slack control device for the hoisting cables of clamshell and other types of boomed rigs and includes a pair of transversely spaced, spring compensated, telescopic units for each hoisting cable. A cable-engaging sheave, which rides over the top of an associated cable, is freely mounted on a shaft extending across the tops of the telescopic units, which are pivotally attached at their bottoms to the deck of the rig at a position intermediate the base of the boom and the winch drums of the rig. The telescopic units pivot toward or away from the winch drums as the angle of the boom is changed.

THE INVENTION This invention relates generally to new and useful improvements in tension control devices for the cables of hoisting rigs and particularly seeks to provide a novel device for eliminating or controlling slack in the hoisting cables of clamshell and other types of boomed rigs.

When a clamshell rig is used for excavating, particularly when used for underwater dredging under murky or roiled water conditions, it is diflicult for the operator to lower the bucket into digging contact with the earth or bottom without permitting slack to form in the hoisting cables as the result of a short overrunning of the winch drums before they can be stopped after digging contact has been made by the bucket. Such periods of cable slack obviously are of an intermittent nature and the degree of slack is variable.

The geometry of these types of rigs makes the control of cable slack quite difficult, because when the boom approaches its flat position the bucket cables are close to the deck of the rig and when the boom is raised the bucket cables are a substantial height above the deck.

Regardless of the position of the boom, slack in the hoisting cables may result in them becoming fouled around the bucket, kinked, crossed over on the winch drums or broken when sudden hoisting tension is applied.

However, the devices constructed in accordance with this invention overcome the above-described problems and provide means for simply and effectively controlling slack in the hoisting cables.

Therefore, an object of this invention is to provide a device for controlling and eliminating the slack in the hoisting cables of clamshell or other types of rigs.

Another object of this invention is to provide a device of the character stated that is adapted to engage a hoisting cable at a position intermediate a winch drum and the end of an associated boom and to take up any slack in the cable by automatically displacing the engaged portion of the cable a distance suflicient to maintain the cable taut.

Another object of this invention is to provide a device of the character stated that includes a pair of transversely spaced, spring compensated, telescopic units having their lower ends pivotally connected to the deck of a rig at a position intermediate the base of the boom and the winch drums and provide at their upper ends with a transice versely extending shaft upon which is freely mounted cable-engaging sheave.

Another object of this invention is to provide a device of the character stated in which its telescopic expansion or contraction is effective to control slack in its associated hoisting cable throughout the full range of useful boom angles.

A further object of this invention is to provide a device of the character stated that includes a link of automatically variable length extending between the upper portion of each telescopic unit and an associated part of the rig boom whereby to cause the telescopic units to pivot toward the boom as it is lowered toward its flat position and to permit the telescopic units to pivot toward the winch drums under the pull of the engaged hoisting cable as the boom is raised toward its highest useful angle of operation.

A further object of this invention is to provide a device of the character stated in which each telescopic unit includes a lubricating oil sump at the bottom thereof and inwardly operating check valves to admit air thereto during elongation of the telescopic units to cause forcible distribution of the oil through spray aperatures in internal telescopic piping to lubricate the relatively moving parts.

A further object of this invention is to provide a device of the character stated in which the bottom of each telescopic unit is provided externally of the lubricant check valve with one or more inwardly operating check valves to permit ready elongation of the telescoping unit when subjected to cable tension and to prevent rapid escape of air from within the unit and thus cushion its contraction Whenever the cable tends to become slack.

A still further object of this invention is to provide a device of the character stated that is readily adaptable to control cable slack either by pulling down or pushing up on the cable.

With these and other objects, the nature of which will be apparent, the invention will be more fully understood by reference to the drawings, the accompanying detailed description and the appended claims.

In the drawings:

FIG. 1 is a vertical section of one fully extended leg of a cable slack control unit constructed in accordance with this invention;

FIG. 2 is an end elevation of the cable slack control unit in its fully extended position;

FIG. 3 is a somewhat schematic side elevation showing the cable slack control unit installed on the deck of a rig in operative association with a hoisting cable when the boom is at a high angle position;

FIG. 4 is a view similar to FIG, 3 but showing the change in postion and contraction of the cable slack control unit when the boom is at a nearly flat postion; and

FIG. 5 is a generally schematic side elevation showing how the cable slack control unit may be adapted for use in rigs having their winch drums both horizontally and vertically separated.

Referring to the drawings in detail, the invention as illustrated is embodied in a cable slack control unit that includes a pair of spaced parallel, telescopic legs generally indicated at 5. Each leg 5 is formed from a top sleeve 6, a first intermediate sleeve 7, a second intermediate sleeve 8, and a bottom sleeve 9 with the intermediate and bottom sleeves being of successively reduced diameter and arranged in telescopic relationship with respect to the top sleeve 6 and to each other. The relative diameters of the several sleeves are such that the sleeves will slide readily with respect to each other without free play.

The bottom of the sleeve 9 is closed by a plate 10 (see FIG, 1) provided with a depending pad eye for pivotal connection to a mounting bracket 12 secured to the deck or base 13 of the associated rig.

Each leg 5 is also provided with a number of inner axially aligned telescopic guide sleeves that include a bottom sleeve 14 having its lower end secured to the plate and its upper end coextensive with the outer sleeve 9; a first intermediate sleeve having its lower end slidably fitted within the upper end of the sleeve 14 and its upper end coextensive with the outer sleeve 8; a second intermediate sleeve 16 raving its lower end slidably fitted within the upper end of the sleeve 15 and its upper end coextensive with the outer sleeve 7; and a top sleeve 17 having its lower end slidably fitted within the upper end of the sleeve 16 and its upper end coextensive with the outer sleeve 6 and secured to a plate 17 that closes the upper end thereof. A lug 18 is affixed to the top of the plate 17 to support a transverse shaft as will be hereinafter more fully described.

The outer sleeve 6, together with its associated inner sleeve 17, is freely slidable without restraint over the intermediate sleeve 7. The top of the sleeve 7 is closed by an annular plate 19 provided with a depending cylindrical spring retainer 20, and the upper portion of the sleeve 15 is similarly closed by an annular plate 21 pro vided with a depending cylindrical spring retainer 22. A compression spring 23 is interposed between the annular plates 19 and 21 and supports the weight of the sleeves 7 and 16. Another compression spring 24 is interposed between the annular plate 21 and the bottom of the sleeve 9 and supports the weight of both the sleeves 8 and 15 and the sleeves 7 and 16 together with the compression spring 23.

The top closure plate 17 and the bottom closure plate 10 each may be provided with one or more inward flow adjustable check valves, symbolically indicated at 24, to freely admit air into the void between the sets of inner and outer sleeves in order to minimize resistance to elongation of the leg 5 under operative conditions, yet enabling contraction of the legs to be cushioned through compression of air in such void.

The lower inner sleeve 14 is at least partly filled with lubricating oil 25 and the center of the bottom closure plate 10 is provided with an inward flow adjustable check valve, symbolically indicated at 26, so that when the leg 5 becomes elongated the valve 26 will open to force the oil, by pressure differential, up through the inner sleeves and out through apertures 27 in the upper sleve 17 for lubrication purposes.

The upper outer sleeve 6 is provided with a strap 28 to which a pad eye is rigidly affixed for attachment to a telescopic position control link as will be hereinafter more fully described.

As mentioned above, two of the telescopic legs 5 are used as a unit to control the slack in a single hoisting cable. When installed, the legs 5 are disposed to either side of the mean axis of the cable and have their tops connected by a transverse shaft 30 which is carried by the lugs 18 and supports a freely rotatable cable-engaging sheave 31 which is also freely slidable along the shaft 30 in order to stay properly aligned with the cable as it traverses its winch drum 32 during winding and unwinding operations. If desired, a safety pulley 33 may be mounted beneath the sheave 31 on straps 34 to prevent the hoisting cable from becoming disengaged from the sheave.

A telescopic spring loaded link 35 extends from the pad eye 29 on each leg 5 to a corresponding pad eye 36 atfixed to the boom 37 of the rig.

In use, the upper sleeves 6, the shaft 30 and its associated sheave 31 and safety pulley 33 are sufficiently heavy to exert a constant downward force on an associated hoisting cable 38 so that if only a small amount of slack occurs in the cable it will be taken up by a downward gravity movement of the sleeves 6. The intermediate sleeves 7 and 8 will remain in their normal elongated or extended positions under the supporting influence of the compression springs 23 and 24. However, when a greater slack occurs in the cable .38 the sleeves6 will become lowered into contact with the sleeves 7 to contract those sleeves and the sleeves 8 until all the cable slack is taken up, Downward movement of the sleeves under abrupt cable slack conditions will be cushioned by the springs 23 and 24, and by compression of the air in the void between the inner and outer sleeves since the check valves 24 remain closed.

As the cable becomes taut through operation of the winch it exerts a lifting effect on the sheave 31 and the sleeves 6 to elongate and pivot the legs to their normal at rest position that will, of course, vary in accordance with the angle of the boom 37. With the boom at a high angle as indicated in FIG. 3, the link 35 has substantially no tension applied to it and the cable 38 has pivoted the legs 5 back toward the winch drum 32. With the boom at a low or nearly fiat angle as indicated in FIG. 4, the link 35 has pivoted the legs 5 forwardly toward the boom, thus lowering the height of the sheave 31 to keep it in slack controlling engagement with the correspondingly lowered cable 38. In such a lowered postion of the boom the legs 5 have become telescoped to nearly their full limit of contraction.

The legs 5, when designed for use with a typical clamshell rig, will be on the order of 14' long when fully extended and on the order of 5' long when fully contracted, thus providing a linear take up of approximately 9'. It should also be noted that due to the forward pivoting of the legs 5 when the boom is nearly flat, the lower rim of the sheave 31 is brought down to a position about 4' above the deck, thus further enhancing control of slack in the cable when it is nearly horizontal.

FIG. 5 of the drawings indicates how the cable slack control device of this invention may be readily adapted for use in connection with those types of rigs in which the hoisting drums are vertically and horizontally spaced and one hoisting cable will be higher than the other in its lead to the end of the boom. In this adaptation the upper unit 5 is pivotally attached to a generally horizontal platform 39 having its rear end pivotally connected as at 40 to the A-frame of the rig and its front end pivotally connected as at 41 to the upper end of a generally vertical link 42 having its lower end pivotally connected to the boom 37 as at 43.

The upper winch drum 44 carries the second hoisting cable 45 which leads over the top of the sheave 31 of the unit 5 which controls cable slack by pushing upwardly aaginst the cable. Of course, in this adptation it will be necessary to include a compression spring in the upper sleeve of the unit 5 and to provide heavier compression springs than those required for the lower unit in order that the upper unit will elongate under spring pressure to take up slack in the cable 45 and will be contracted against the spring pressure as the cable becomes taut. The telescopic link 35 extends between the upper sleeve of the upper unit 5 and a suitable location on the A-frame of the rig. As the boom 37 is raised or lowered the position of the platform 39 and its associated control unit 5 will be changed correspondingly so that the control unit will remain properly effective.

It is of course to be understood that variations in arrangements and proportions of parts may be made.

We claim:

1. In a hoisting rig wherein is provided a base, a boom pivotally connected at its lower end to said base, a winch drum mounted behind said boom and a hoisting cable extending from said winch drum to and over the upper end of said boom; the combination of a generally vertical plural-section telescopic cable slack control unit having its lower end pivotally connected to said base at a position intermediate the lower end of said boom and said winch drum and having its upper end operably engaged with said hoisting cable, the telescopic sections of said cable slack control unit being sufliciently heavy to exert a downward force on said hoisting cable whereby to automatically contract and take up slack in said hoisting cable as it occurs and to become elongated as tension is again applied to said hoisting cable, and means connecting the upper section of said telescopic slack control unit with an adjacent part of said boom whereby to cause said telescopic slack control unit to pivot forwardly as said boom is lowered and to permit said slack control unit to pivot rearwardly as said boom is raised.

2. The combination of claim 1 additionally including a cable-engaging sheave at the top of said telescopic slack control unit.

3. The combination of claim 2 in which said slack control unit contains at least three concentric telescopic sections and in which spring means are provided for counterbalancing any intermediate section thereof.

4. The combination of claim 3 additionally including a lubricating oil reservoir, oil distributing means and means for causing oil to be forced through said distributing means to lubricate said telescopic sections during elongation or contraction of said telescopic unit.

5. The combination of claim 3 in which said slack control unit comprises two laterally spaced plural-section telescopic legs connected across their tops by a transverse shaft which rotatably supports said cable-engaging sheave.

6. The combination of claim 5 in which each leg includes four external telescopic shells of successively reduced diameter from top to bottom, four internal telescopic shells of successively reduced diameter, from bottom to top, a compression spring carried Within the bottommost of said external shells for resiliently supporting the weight of the two intermediate external and internal shells, and a compression spring carried within the lower intermediate external shell for resiliently supporting the weight of the upper external and internal intermediate shells upon the lower external and internal intermediate shells, the top external and internal shells being unsupported and freely slidable with respect to the said upper external and internal intermediate shells.

'7. 'lhe combination of claim 6 additionally including a closure plate for the bottoms of said bottommost external and internal shells, at least one inward-flow check valve mounted in said bottom closure plate to admit air into the void between said external and internal shells whenever said leg undergoes elongation whereby to lessen resistance to such elongation and to prevent air from rapidly escaping from said void whenever said leg undergoes contraction whereby to additionally cushion the contraction thereof, a closure plate for the tops of the topmost of said external and internal shells, and at least one inward-flow check valve mounted in said top closure plate to function in the same manner as the check valve in said bottom closure plate.

8. The combination of claim 2 in which said telescopic slack control unit is pivotally mounted on a generally horizontal platform having its rear end pivotally connected to the frame of said rig and its front end pivotally connected to the upper end of a generally vertical link the lower end of which is pivotally connected to an adjacent part of the boom.

References Cited UNITED STATES PATENTS 3,096,078 7/1963 Steingass 254- HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R. 2l2l44; 254-439 

